Turbo-molecular pump

Abstract

Disclosed is a turbo-molecular pump, which comprises a rotor including a first cylindrical body formed with a part of a plurality of rotating blades arranged in multistage, a second cylindrical body integrally connected to an outer peripheral region of a downstream end of the first cylindrical body and formed with the remaining rotating blades, and a stress-releasing protrusion extending from the downstream end of the first cylindrical body along a direction of a rotation axis of the rotor. The turbo-molecular pump of the present invention can reduce a stress in the downstream end of the first cylindrical body.

1. A turbo-molecular pump comprising:
 a rotor which is formed with a plurality of rotating blades in a multistage arrangement, and adapted to be rotated at a high speed so as to perform an evacuation operation, said rotor including
 a first cylindrical body formed with a part of said plurality of rotating blades; 
 a second cylindrical body integrally connected to an outer peripheral region of a downstream end of said first cylindrical body, and formed with the remaining rotating blades; 
 a screw rotor portion which extends from said second cylindrical body along a direction of a rotation axis of said rotor; and 
 a stress-releasing protrusion which extends from the downstream end of said first cylindrical body along the direction of the rotation axis of said rotor; and 
 
 a first screw stator which extends to have a distal edge located between said screw rotor portion and said protrusion; and 
 a second screw stator which extends to have a distal edge located on an opposite side of said screw rotor portion with respect to said first screw stator portion. 
 
     
     
       2. The turbo-molecular pump as defined in  claim 1 , wherein said first cylindrical body is formed in a conical shape. 
     
     
       3. The turbo-molecular pump as defined in  claim 1 , wherein said first screw stator has an upstream end formed with a convex portion protruding toward said protrusion; and
 the inner peripheral surface of said protrusion is formed with a concave portion in opposed relation to said convex portion. 
 
     
     
       4. A turbo-molecular pump comprising a rotor which is formed with a plurality of rotating blades in a multistage arrangement, and adapted to be rotated at a high speed so as to perform an evacuation operation, said rotor including:
 a first cylindrical body formed with a part of said plurality of rotating blades; 
 a second cylindrical body integrally connected to an outer peripheral region of a downstream end of said first cylindrical body, and formed with the remaining rotating blades; and 
 a stress-releasing protrusion which extends at said rotor from the bottom of the downstream end of said first cylindrical body along a direction of a rotation axis of said rotor; and 
 a screw stator which extends to have a distal edge located between said second cylindrical body and said protrusion, so that an outer peripheral surface of said screw stator forms thread groove pumping means in cooperation with an inner peripheral surface of said second cylindrical body 
 wherein said screw stator has an upstream end formed with a convex portion protruding toward said protrusion; and 
 the inner peripheral surface of said protrusion is formed with a concave portion in opposed relation to said convex portion. 
 
     
     
       5. The turbo-molecular pump as defined in  claim 4 , wherein said first cylindrical body is formed in a conical shape.